* openbsd: enable IPv6 PTMUD DoS prevention.  validates TCP6/UDP6 PMTUD   by existence of connected pcb.
* openbsd: enable IPv6 PTMUD DoS prevention.  validates TCP6/UDP6 PMTUD
  by existence of connected pcb.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame